1. Field of the Invention
The invention relates to a radiation detector and, more particularly, to an apparatus for simultaneously deriving multiple images from a focal plane array over different spectral bands.
2. Discussion of the Prior Art
In the prior art, systems that generate multiple spectral bands have either employed scanning sensors or staring sensors. Scanning sensors are readily adaptable to generating multiple spectral bands. However, scanning sensors are large, have low update rates, and are mechanically complex, making them unsuitable for many applications. Staring sensors are small, have fast update rates, and are mechanically simple. However, in order to obtain multiple spectral bands, the prior art combined staring sensors with multiple arrays, checkerboard filters and moving focus spectrometers. These modifications added to the size of the prior art systems, while decreasing the speed and simplicity of those systems.
The intensity at each point in the image from a staring focal plane array (FPA) camera is proportional to the radiant intensity, over the spectral band of the FPA, of the corresponding point in the object scene. For example, with an FPA sensitive over the spectral band from 3 to 5 microns the camera will generate a single medium wave (MW) IR image. In some applications it is desirable to have two, spectrally distinct, images of the scene: for example one image showing the scene over one band, for example 3.0-3.8 microns, and another showing the scene over another, different band, for example 4.2-5.0 microns.
Therefore, it is a motive of the invention to simultaneously derive two different spectral band images of the object scene from one camera sensitive over both spectral bands.